When a large-scale disaster such as a big earthquake occurs, a general line such as a cellular phone may not be able to use by a system failure and a traffic concentration in a disaster area. In this case, a way for emergency contact from a disaster victim to fire-fighting and disaster prevention related parties is halted. When a way for emergency contact is halted, information gathering of such as the position of, the number of and the situation of disaster victims becomes difficult for fire-fighting and disaster prevention related parties. Accordingly, lifesaving within a survival time limit of 72 hours of initial motion becomes difficult.
In Japanese Patent Application Laid-Open No. 2009-124448, a portable communication system including a plurality of mobile terminals and an information server is proposed. In this portable communication system, in a case where a plurality of mobile terminals are outside the communication range of a wireless base station, by these mobile terminals performing short-distance communication, the communication range is extended, and information is shared. The information server is connected to a communication network of an independent type. When information is transmitted by short-distance communication from at least one mobile terminal to another mobile terminal located in the communication range, the communication network receives and holds information transmitted from the mobile terminal located in the communication range via a wireless base station. Then, according to a request from the mobile terminal located in the communication range, the communication network transmits the held information.
As a result, each mobile terminal which is outside the communication range of the wireless base station can share disaster information. Accordingly, even when a mobile terminal which exists within the disaster-stricken area cannot transmit disaster information because a communications infrastructure such as a communication network is shut down by a disaster, mobile terminals become to be able to communicate each other directly. That is, disaster information can be sent from outside of the communication range to the communication range.
In Japanese Patent Application Laid-Open No. 2003-272071, a monitoring system having a transmission means and a converting means is proposed. The transmission means receives an emergency notification wirelessly transmitted from a mobile terminal, and transmits this emergency notification to a monitoring center via a transmission line. The converting means converts the emergency notification from the mobile terminal into a wireless system suitable for a communication device of a public institution, and transmits it to the public institution.
However, when a communication failure occurs to a communication line which is usually used, systems disclosed by Japanese Patent Application Laid-Open No. 2009-124448 and Japanese Patent Application Laid-Open No. 2003-272071 mentioned above have a problem that they cannot be used any more. That is, they cannot perform communication about an emergency using a line besides a communication line which is usually used.